Total internal confinement of magnetic field

[Baluncore]

If you wouldn't mind, do you think you could please comment on this:

In what respect? The coupling of coils is "mutual inductance". http://en.wikipedia.org/wiki/Inductance#Coupled_inductors_and_mutual_inductance

Being orthogonal, internal toroid flux and the internal part of the external flux are independent. On the other hand, a bifilar wound toroidal transformer would have very tight coupling between windings. They are used for RF impedance matching and coupling transformers.

The coupling coefficient between two coils can be adjusted from -1 through zero to +1 by using a variometer. A variometer can also be used as a variabe inductor by connecting the two coils in series. http://www.g3ynh.info/comps/Vari_L.html

 

[tim9000]

On the other hand, a bifilar wound toroidal transformer would have very tight coupling between windings.

I assume you mean you wind the transformer with the primary and secondary wires together at once.

The coupling coefficient between two coils can be adjusted from -1 through zero to +1 by using a variometer. A variometer can also be used as a variabe inductor by connecting the two coils in series. http://www.g3ynh.info/comps/Vari_L.html

Very interesting page, but I still don't quite understand the coupling coefficient completely yet.

In what respect?

Well the formula L = N/reluctance, where N is the amount of turns on inductor 1, is that the inductance for just L11, or for 'L11 + L12'?
And also it's getting the K in the first place I'm unsure about, how do you calculate or measure flux12 or flux 21?
Thanks

 

[Baluncore]

And also it's getting the K in the first place I'm unsure about, how do you calculate or measure flux12 or flux 21?

If you are a beginner to EM then I really think you should avoid calculating mutual inductance. There are a few analytic solutions, but they require simple geometry and assume a surrounding environment of free space. Numerical solutions are available using finite element methods.

L = N/reluctance, where N is the amount of turns on inductor 1, is that the inductance for just L11, or for 'L11 + L12'?

Further discussion of mutual inductance should be in that other thread. Keep this thread for toroids.

 

[tim9000]

If you are a beginner to EM then I really think you should avoid calculating mutual inductance. There are a few analytic solutions, but they require simple geometry and assume a surrounding environment of free space. Numerical solutions are available using finite element methods.

I'm not so much a beginner as someone who needs to rapidly refresh what I learned years ago and build on it. FEA?? Really...Are you saying that there is no simple way to calculate the L12 and L21 (specifically the flux of Fi12 and Fi21)? Could you please comment as to this and about whether the inductance formula is for mutual and self inductance, or just self inductance, on the other thread?
Greatly appreciated.

 

[Baluncore]

Mutual inductance has little to do with “total internal confinement of magnetic field” but; Each and every dw of the winding on L1 generates a dipole vector field that interacts with each and every other dw of L1 itself, of L2 somewhere else with some orientation and every other patch of the environment. So you have a huge scattering matrix that describes the cross coupling of the entire system. It can get very complex when there are phase shifts due to propagation delays.

There are a few algebraic solutions for mutual inductance of basic geometrical situations. I would suggest you find a copy of “Inductance Calculations” by G.W.Grover. Use http://www.bookfinder.com/ to locate a low cost copy, or maybe a new Dover Publications reprint.

 

[tim9000]

Mutual inductance has little to do with “total internal confinement of magnetic field” but; Each and every dw of the winding on L1 generates a dipole vector field that interacts with each and every other dw of L1 itself, of L2 somewhere else with some orientation and every other patch of the environment. So you have a huge scattering matrix that describes the cross coupling of the entire system. It can get very complex when there are phase shifts due to propagation delays.

when you say 'dw' I assume you mean infinetesimally small part of the winding.
Right, so you can't really measure mutual flux Fi12 or Fi21, you need to work it out algebraically from the specific geometry?
And the standard inductance formula is just for L11 = N/Reluc and mutual inductance is much more complex to determine?
I surtainly will hunt for the book, cheers for the recomendation?